Atomic Layer Deposition (ALD) is a high-quality thin-film deposition technique based on sequential, self-limiting surface reactions. Atomic layer deposition works by sequentially exposing a substrate to at least one reactant vapor or solution and, for example, maintaining the substrate temperature in a certain range, depending on the deposited materials. With each vapor exposure a self-limiting reaction occur on the surface of the substrate if the substrate temperature is within a certain range. In some cases, the substrate may be at ambient temperature and the energy necessary for the surface reaction may be supplied, e.g., via plasma or ions). ALD can control the thickness of deposited films at the level of an atomic layer. Thus films deposited by ALD tend to be uniform over large areas. In addition ALD allows deposition of conformal films on structures having very high aspect ratios (e.g., >10). A wide variety of materials may be deposited by ALD, including semiconductors, metals, oxides, nitrides, and other materials
ALD techniques can thus deposit thin films one atomic layer at a time, in a “digital” fashion. Such “digital” build-up of material greatly simplifies thickness control, thus reducing both the complexity and cost of thin film deposition.
Many industries, such as the optoelectronics industry, can benefit from the high uniformity, high aspect ratio conformal coating abilities and low cost of ALD. Unfortunately, prior art ALD systems have mostly been made for semiconductor wafer processing, which is oriented to batch processed wafer handling systems. Although existing ALD systems are suitable for the semiconductor industry, they are unsuitable for high volume manufacturing of large area devices such as photovoltaic cells. Current ALD systems are typically designed to coat small area wafers. Scaling up systems that coat a small area at a time might not be practical for coating large area sheets, panels or rolls of material. ALD may be too slow if many cycles are required to deposit the desired film thickness and each reaction step is rate-limited.
Thus, there is a need in the art, for a high throughput atomic layer deposition method and system.